SAN FRANCISCO, CALIF.   - Internet giants Twitter, Facebook and Google appear to be increasing enforcement of their policies in the run-up to U.S. Election Day.    

That has put them on a collision course with Republicans, who are calling out the companies for making allegedly biased decisions to restrict conservative speech.     

Twitter, where President Donald Trump has more than 87 million followers, has recently placed warnings on some of the president’s tweets about topics such as the coronavirus and voting by mail.    

Last week, Twitter temporarily blocked a tweet from Trump’s campaign over an article about his Democratic challenger, Joe Biden. Facebook also took measures to counter the sharing of that article.  
 
Over the weekend, Twitter blocked a post from Scott Atlas, a special adviser to the president, who in a Tweet questioned the effectiveness of widespread mask orders.  
 
The companies are taking measures on other speech as well: YouTube, which is owned by Google, and TikTok have cracked down on the QAnon conspiracy theory. Facebook said it would remove Holocaust denial content.  
 
Facebook will suspend new political ads from Oct. 27 through election night. Google said it would limit the way political ads can be targeted. Twitter, last year, announced it would not accept political and issues ads. 

Why are the companies taking these measures now?  

Experts say Facebook and Twitter, in particular, are under pressure to better monitor disinformation than they did in the run-up to 2016.   

“The thing about the upcoming election, as a colleague put it, it's kind of like the disinformation Super Bowl,” said Lisa Kaplan, chief executive of the Alethea Group, which consults with companies and organizations about disinformation. “It’s a big event.”    

Not long ago, the internet companies let their users — and advertisers — do the talking without much interference.  
 
After the 2016 U.S. election, they were criticized for not doing enough to stop misinformation on their services, including letting foreign-sponsored networks run online influence campaigns. 

Some criticize the companies as doing too little, too late, to stop the flood of misinformation on their sites.  

The companies “need to accept that they have to be the ones to deal with these issues,” rather than being “the enablers as they were previously,” said Ann Ravel, former chair of the Federal Election Commission. A Democrat, she is running for state senate in California.   

Others criticize the firms’ decisions as biased, curtailing conservative speech in a way that could affect the outcome of the U.S. election.     

Republican senators have called for the CEOs of Twitter and Facebook to testify about their policies. Trump’s top aide, Mark Meadows, told "Fox & Friends" on Monday that the internet firms are biased against conservatives and may be subject to new lawsuits.  

But it isn’t just some Republicans who are frustrated. Lawmakers from both parties are considering changing the laws that say the companies are not responsible for the speech other people publish on their sites.     

Take that protection away and the companies will be destroyed, said Ken Paulson, director of the Free Speech Center at Middle Tennessee University.     

“You either have a very small service,” he said, “or you are going to have to run the risk of having content that is disturbing, confusing and that misinforms people. There is really two choices. Congress can’t do much about it except try to destroy Twitter and Facebook.”         

It’s high stakes for internet firms as Election Day 2020 approaches to prove they are good stewards of the powerful services they have built.